1. Field of the Invention
The present invention relates to fluorenyl compounds, to the corresponding bridged bis-fluorenyl metallocenes and to their use as catalyst components in processes for the polymerization of olefins.
2. Description of Related Art
Many metallocene compounds are known to be active as catalyst components in the olefin polymerization reactions. A particular class of these metallocenes is that of stereorigid metallocene compounds having two cyclopentadienyl ligands joined by means of a bridging group which gives stereo-rigidity to the molecule. These compounds, which are generally referred to as bridged metallocenes, can be prepared from the corresponding bridged ligands.
While compounds having two bridged ligands of the indenyl type are widely known, there are only a few disclosures of compounds having two bridged fluorenyl groups.
In Japanese Patent Application Publication No. 1 249 782, it is described the preparation of the potassium salt of the bis(fluorenyl)dimethylsilane to be used for preparing organolantanide hydrides. These compounds are useable as catalysts for the hydrogenation of olefins of every type and for the polymerization of ethylene.
A process for the preparation of bridged fluorenyl-containing compounds is disclosed in EP-A-512,554. With this process 1,2-bis(9-fluorenyl)ethane, 1,3-bis(9-fluorenyl)propane, bis(9-fluorenyl)methane, 1,2-bis(9-fluorenyl)-2-methyl-ethane and bis(9-fluorenyl)-dimethyl-silane were prepared.
Bridged bis-fluorenyl compounds are disclosed in EP-A-524,624. A number of ethylidene, propylidene, methylethylidene and, dimethyl-silyl-bridged bis-fluorenyl compounds were prepared.
EP-A-604,908 discloses a class of bis-fluorenyl compounds bridged with a one-atom-bridge. Only dimethyl-silyl-bridged bis-fluorenyl compounds are exemplified. These metallocenes are useful as catalyst components for the polymerization of olefins and, expecially, for the preparation of high molecular weight atactic polypropylene.
Diphenyl-silyl and dimethyl-tin bridged bis-fluorenyl metallocenes are disclosed in EP-A-628,565. These compounds are used in the preparation of isotactic polypropylene.
New metallocenes having two bridged fluorenyl rings which can be advantageously used as catalytic components for the polymerization of olefins and, expecially, for the preparation of high molecular weight atactic polypropylene with improved yields, have been surprisingly found.
Therefore, in accordance with an aspect of the present invention, there are provided metallocene compounds having two fluorenyl ligands bridged with a single silicon or germanium atom, said atom having two substituent groups containing a total of at least four carbon atoms.
According to another aspect of the present invention there is provided a method for the preparation of the above described metallocene compounds.
Still further in accordance with the present invention, there are provided bis-fluorenyl ligands bridged with a single silicon or germanium atom, said atom having two substituent groups containing a total of at least four carbon atoms.
Furthermore, according to another aspect of the present invention, there are provided catalysts for the polymerization of olefins comprising the bis-fluorenyl metallocenes of the invention.
According to a still further aspect of the present invention there is provided a process for the polymerization of olefins comprising the polymerization reaction of at least an olefinic monomer in the presence of such catalysts.